In the field of photographic light-sensitive materials there is a growing demand for increasing still further photographic speed.
Referring to, for example, radiographic light-sensitive materials, as the number of medical X-ray examinations has increased in recent years, a reduction in the exposure dose has been strongly demanded in medical circles, and by general international opinion. In order to meet this demand, state-of-the-art photographic technology enabling the formation of an adequately high-quality radiographic image even with a small exposure dose is essential, and for this reason, the development of photographic techniques with enhanced precision, which obtain a high-definition image with only a slight exposure dose, i.e., development of photographic techniques for an even higher photographic speed, have been required.
If a proper sensitization technique is applied, photographic speed of a silver halide can be further be increased while maintaining the grain size being kept intact. i.e., with covering power being unchanged. In this regard, many proposals have until now been reported which include, for example, a method of incorporating a development accelerator, such as a thioether, into an emulsion: in the case of spectrally sensitizing a silver halide emulsion, a method of supersensitizing the silver halide emulsion by using appropriately combined sensitizing dyes: improving techniques for spectrally sensitizing dyes: and the like. These methods, however, are hard to be considered always widely applicable to high-speed silver halide light-sensitive photographic materials: high-speed silver halide emulsions, because of being as chemically sensitized as is possible, are liable to be fogged during their preservation, if the above methods are used.
Furthermore, in the field of medical radiography, orthochromatic light-sensitive materials sensitive to the wavelength range of from 540 to 550 nm, which have been achieved by orthochromatic sensitization of conventional regular-type light-sensitive materials sensitive to the wavelength region of 450 nm, or those panchromatic or infra-red sensitive photographic materials, which are sensitive to spectral region of 630 nm to 830 nm like photosensitive materials for laser printer, have come into use. The light-sensitive material thus sensitized becomes so wide in the wavelength region range to which it is sensitive, and the sensitivity is so high that the exposure dose can be reduced, lessening the affect on the human body. Thus, the sensitization by sensitizing dyes is a very effective sensitization means, but has problems yet to be solved: for example, the problem that sufficient sensitivity cannot be obtained, depending on the type of photographic emulsion used.
On the other hand, the quantity of silver halide photographic materials processed by every photo-finisher has been increasing year by year, resulting in a demand for a still greater increase in the speed of processing: i.e., increasing the number of photographic sheets processed within a predetermined period of time.
The above tendency can also be seen in the field of radiographic light-sensitive materials such as, for example, medical X-ray films. With the rapid increase in the incidence of medical diagnoses, due to the strict enforcement of regular physical examinations, checkup items have been increased in order to make the diagnosis even more accurate, thus resulting in the increase in the number occasion for the radiographic images to be taken.
It is of course advantageous for automatic processing apparatus to speed up the processing of X-ray films, because whilst should the processors operate at the same capacity, its compact size contributes to space-saving.
However, although the merits of rapid processing are great, as mentioned above, there are a lot of problems yet to be solved: (a) insufficient densities (decrease in the speed, contrast and the maximum density), (b) insufficient fixation, (c) insufficient washing of film, and (d) insufficient drying of film, and the like, of which insufficient fixation and insufficient washing of film lead to discoloration of the film during the preservation period of the developed films; thus causing deterioration in the quality of the processed film.
It has been known in the art that decreasing the thickness of layers which constitute the photographic material, i.e., `photographic component layer`, and hardening the photographic constituting layer to a certain extent make it possible to process a light sensitive silver halide photographic material at a high speed. It has also been possible to produce a light sensitive photographic material suitable for rapid processing by reducing of the total amount of silver to be used.
Thus, reducing the thickness, increasing the hardness of the film, or reducing the amount of silver used can enhance adaptability of the photographic material to rapid processing, however, image quality still remains to be a problem. That is, it is not too much to say that only images with extremely deteriorated image qualities have been obtainable, and that it has been impossible to design a system suitable for practical use.
Particularly, most important of all, when a photographic material thus constituted is processed by super rapid process, it has usually been the case that only images with extremely deteriorated graininess can been obtained. For example, referring to adaptability of this technique to X-ray photography for medical use, deteriorated graininess, for example, can cause difficulty in diagnostic judging of a focus, which makes it almost impossible to apply this technique to practical use.
In recent light-sensitive materials, such as radiographic films, prepared by coating a light-sensitive silver halide emulsion on both sides of a support base for the purpose of image quality improvement, there is a tendency that increased amount of sensitizing dyes or other dyes for higher image definition and higher photographic speed are used. As a result, the problem, that considerable amount of dye remains inside the processed light-sensitive material, the so-called dye-stain trouble, which had not been a matter of concern in the in the conventional processing systems, has become increasingly likely to occur, a large drawback to super-rapid processing.